JP2010507211A - End cap encapsulant for electrochemical cells - Google Patents

Abstract

An end cap seal assembly for an electrochemical cell such as an alkaline cell is disclosed. The end cap assembly comprises a metal support disk and underlying insulating sealing disk and a metal end cap overlying the metal support disk. The edge of the end cap and metal support disk is captured by the crimped edge of the insulating sealing disk. The support disk has a downwardly extending wall with at least one aperture therethrough. The insulating disk is preferably composed of a polyetherurethane material and may have a slanted downwardly extending wall forming a rupturable membrane which underlies and abuts the inside surface of the downwardly extending wall of the support disk. A portion of the rupturable membrane underlies and abuts the aperture in the downwardly extending wall of the support disk. The rupturable membrane pushes through said aperture and ruptures when gas pressure within the cell exceeds a predetermined level.

Description

  The present invention relates to an end cap assembly for sealing electrochemical cells, particularly alkaline cells. The present invention relates to a rupturable device in an end cap assembly that allows gas to flow from the inside of a battery to the outside world. The present invention relates to a rupturable device comprising a polyetherurethane material.

  Conventional electrochemical cells, such as alkaline batteries, are formed of a cylindrical housing having an open end and an end cap assembly, and the end cap assembly is at the open end to seal the housing. Inserted. Conventional alkaline batteries typically include an anode containing zinc, a cathode containing manganese dioxide, and an alkaline electrolyte containing an aqueous potassium hydroxide solution. After the battery contents are supplied, the battery is closed by crimping the housing edge over the end cap assembly, providing a seal to the battery. The end cap assembly comprises an exposed end cap that functions as a battery terminal and a typically plastic insulating plug that seals the open end of the battery housing. The problem with the design of various electrochemical cells, especially alkaline cells, is that the battery generates gas when it continues to discharge to a certain extent, usually beyond the point where the battery's effective capacity is nearly exhausted. There is a tendency.

  Electrochemical cells, particularly alkaline cells, can include a rupturable venting mechanism having a rupturable diaphragm or rupturable membrane in the end cap assembly. The rupturable diaphragm or membrane may be formed in a plastic insulating member, for example as described in US Pat. No. 3,617,386. Such a diaphragm is designed to rupture when the gas pressure in the cell exceeds a predetermined level. The end cap assembly may include a vent hole for gas to flow out when the diaphragm or membrane ruptures. The end cap assembly disclosed in U.S. Pat. No. 3,617,386 discloses a grooved ruptureable sealing diaphragm and a separate metal contact disk between the end cap and the sealing diaphragm. ing. The end cap assembly disclosed in the reference is not designed to withstand radial compressive forces and also leaks when the battery is exposed to extremes in warm and cold climates. There is a tendency.

  In order to provide a seal, the latest prior art discloses an end cap assembly having a metal support disk inserted between the end cap plate and the insulating member. This separate metal support disk can be compressed radially when the edge of the battery housing is crimped onto the end cap assembly. The insulating plug typically extends from the center of the battery toward the battery housing and is in the form of a plastic insulating disk that electrically insulates the metal support disk from the battery housing. The metal support disk may have a highly convoluted surface, such as shown in US Pat. No. 5,759,713 or 5,080,985, so that the end cap assembly The volume can withstand a high degree of radial compression while the battery housing edge is crimped around the end cap assembly. As a result, the end cap assembly is always mechanically sealed.

  The prior art discloses a ruptureable vent membrane that is integrally formed as a thin region within an insulating disk contained within an end cap assembly. Such venting membranes are usually oriented so that they lie in a plane perpendicular to the longitudinal axis of the cell, for example as shown in US Pat. No. 5,589,293. In U.S. Pat. No. 4,227,701, the rupturable membrane is formed by an annular "slit or groove" disposed in the arm of an insulating disk that is inclined with respect to the longitudinal axis of the battery. The insulating disk is slidably mounted on an elongated current collector that penetrates the insulating disk. As the gas pressure in the cell increases, the central portion of the insulating disk slides upward toward the end cap of the cell, thereby causing the thin film to “groove” and eventually rupture. U.S. Pat. Nos. 6,127,062 and 6,887,614 B2 disclose an insulating sealing disk and an inclined rupturable membrane integrally formed therein. The portion of the rupturable membrane in the sealing disk contacts the opening in the metal support disk above it. As the gas pressure in the cell increases, the membrane ruptures through the opening in the metal support disk, thereby releasing the pressure of the gas traveling to the external environment.

  In US Pat. No. 6,887,614, the rupturable membrane is in contact with a hole in the metal support disk above it. In US Pat. No. 6,887,614, there is an undercut groove below the membrane. The groove surrounds the longitudinal axis of the battery. The groove forms a thin film portion at the bottom that bursts through a hole in the overlying metal support disk when the cell's internal gas pressure reaches a predetermined level. To do. In the design shown in US Pat. No. 6,887,614, there is an insulating washer that separates the exposed end cap from the battery housing. Such a design has the disadvantage of requiring a further component, i.e. an insulating washer that needs to be inserted into the end cap assembly. The edge of the end cap is located on the shoulder of the battery housing and is separated from the housing by a washer. This allows the end cap to be tampered with, that is, the end cap can be easily removed from the battery and more easily touched by the battery contents.

  The rupturable membrane is formed in an insulating sealing disk as shown in US Pat. No. 4,537,841, US Pat. No. 5,589,293, and US Pat. No. 6,042,967. It may take the form of one or more “islands” of thin-walled material. Alternatively, the rupturable membrane may be in the form of a thin portion surrounding the longitudinal axis of the battery, as shown in US Pat. No. 5,080,985 and US Pat. No. 6,991,872. Can do. The surrounding thin-walled part forming the rupturable membrane is a slit or groove in an insulating disk as shown in US Pat. No. 4,237,203 and US Pat. No. 6,991,872. Can take the form of Also, the rupturable membrane is a separate polymer sandwiched between a metal support disk and an insulating disk and facing an opening therein, as shown in US Patent Application Publication US 2002/0127470 A1. It may be a film. As shown in US Pat. No. 3,314,824, a tapered or other protruding member can be directed over the rupturable membrane to assist in rupturing the membrane. When the gas pressure in the battery becomes excessive, the membrane expands and ruptures upon contact with the tapered member, so that the gas in the battery flows out to the outside through openings in the overlying terminal end caps. it can.

A separate metal support disk that typically includes a convoluted surface as shown in US Pat. Nos. 5,080,985 and 5,759,713 has been included in the end cap assembly. . The metal support disk supports the plastic insulating seal and withstands high radial compression forces that can be applied to the end cap assembly while crimping the edge of the housing around the end cap assembly. Even when the gas pressure in the battery reaches a high level, for example, a high level exceeding 689.4 × 10 ⁴ Pa (1000 psig), the peripheral edge of the end cap assembly and the battery housing due to the high radial compression force The seal along the line can be maintained.

  U.S. Pat. No. 4,537,841 shows a plastic insulating sealing plug or disk for closing the open end of a cylindrical alkaline battery. On top of the insulating seal is a metal support disk. The plastic insulation seal has a central hub and is integrally formed with a radial arm extending radially from the hub to the casing wall of the cell. An “island” type rupturable membrane is integrally formed within its radially extending arm of the insulating seal. An “island” -type rupturable membrane is formed by embossing or compressing a portion of the radially extending arm of the insulating seal to form a small circular thin-walled island portion. The island portion is designed to rupture when the gas pressure in the battery reaches a predetermined level. The island-type rupturable membrane shown in this reference is at the same height as the radially extending arm of the insulating seal, i.e. it lies in a plane perpendicular to the central longitudinal axis of the cell. . The upper surface of the thin, rupturable membrane (facing the open end of the cell) is approximately level with the upper surface of the radially extending insulating arm. While this design is effective, it limits the space available between the rupturable membrane and the metal support disk to a small one. When a battery is intentionally exposed to harsh conditions, such as being exposed to a flame, the temperature and gas evolution inside the battery can increase very rapidly as a result. Under such extreme conditions, the membrane softens, and the membrane may “swell” without rupturing, and the space between the membrane and the metal support disk may be small.

  In view of improvements in gassing inhibitors, particularly the use of multiple gassing inhibitors, current alkaline batteries may be designed to vent at a somewhat lower pressure than in the past. That is, there is a tendency to reduce the operating pressure on the design for the degassing mechanism in the alkaline battery. The design degassing pressure drop imposes design challenges. When “island” type ruptureable membranes are used to trigger the venting mechanism, using conventional molding techniques such as injection molding, how thin such membranes can be molded There are practical limits. Also, depending on the size of the battery, there is a limit to the surface area available for such membranes. Also, when conventional materials such as nylon 66 are used in plastic insulation sealing plugs, the thin ruptureable membrane portions from such materials are required to achieve rupture at low pressure thresholds. It becomes more difficult to form a thin thickness. Since the ultimate tensile strength of such materials is high, a thin film thickness is required.

U.S. Pat. No. 3,617,386 US Pat. No. 5,759,713 US Pat. No. 5,080,985 US Pat. No. 5,589,293 US Pat. No. 4,227,701 US Pat. No. 6,127,062 US Pat. No. 6,887,614 B2 US Pat. No. 6,887,614 U.S. Pat. No. 4,537,841 US Pat. No. 6,042,967 US Pat. No. 6,991,872 U.S. Pat. No. 4,237,203 US Patent Application Publication US 2002/0127470 A1 US Pat. No. 3,314,824

  Accordingly, it is desirable to have an end cap assembly that seals the battery and resists leakage even when the battery can be exposed to extremes in both warm and cold climates.

  It would be desirable to have a reliable, burstable venting mechanism within the end cap assembly that operates and functions properly when the battery is exposed to harsh conditions.

  It is desirable that the end cap assembly can prevent tampering, that is, it cannot be easily removed from the end cap assembly.

  It is desirable that a breachable venting mechanism be easily manufactured and reliable so that venting occurs at a specific predetermined pressure level.

  The present invention relates to an electrochemical cell, such as an alkaline cell, comprising an end cap assembly inserted into an open end of a cylindrical housing (casing) for the cell. In one aspect, when the battery is viewed from a vertical position with the metal support disk up, the end cap assembly includes a metal support disk and an insulating sealing plug (insulating sealing disk) under the metal support disk. It has. The end cap assembly also includes a terminal end cap disposed on the metal support disk.

  The metal support disk is preferably formed of a single metal structure disk having a convoluted surface and at least one vent opening through the surface. When the battery is viewed from a vertical position with the end cap assembly facing up, the insulating sealing disk has a convoluted surface, a portion of which surface is below the vent opening in the metal support disk. is there. The portion of the insulating sealing disk below the opening preferably has a groove on its inner surface facing the cell interior. The groove has an open end and a closed bottom on the opposite side, the bottom of the groove forming a thin, ruptureable membrane. The rupturable membrane is in contact with the opening in the metal support disk. As the gas pressure in the battery increases, the rupturable membrane ruptures through the opening, thereby releasing gas directly into the surrounding environment through the opening.

  The insulating sealing disk includes a plastic material having a downwardly extending wall that is inclined at an angle of less than 90 degrees from the central longitudinal axis of the battery and not parallel to the longitudinal axis. . When the battery is viewed from a vertical position with the end cap assembly facing up, the downwardly extending wall of the insulating disk has a low point on the surface of the insulating disk that is closer to the interior of the battery from a high point on the surface of the insulating disk. It extends downward toward the point. The metal support disk also has a downwardly extending wall inclined at an angle of less than 90 degrees from the central longitudinal axis of the battery. When the battery is viewed from a vertical position with the end cap assembly up, the downwardly extending wall of the metal support disk extends downward from a high point on its surface. There is at least one opening in the downwardly extending wall of the metal support member that contacts the rupturable membrane. Preferably, the downwardly extending wall of the insulating sealing disk can be inclined at an angle between about 35 and 80 degrees from the central longitudinal axis of the battery. The lower extending wall of the overlying metal support disk is desirably inclined at the same angle as the lower extending wall of the insulating sealing disk, preferably between about 35 and 80 degrees from the central longitudinal axis of the cell. is doing. Thereby, the part of the rupturable membrane of the downwardly extending wall of the insulating sealing disk contacts the opening in the downwardly extending wall of the metal support disk and is flush with the opening. The downwardly extending wall of the insulating sealing disk is flush with or substantially flush with the underlying downwardly extending wall of the metal support disk.

  The groove on the inner surface of the downwardly extending wall of the insulating sealing disk that forms part of the rupturable membrane is preferably made to surround the center of the insulating disk. At least the portion of such surrounding ruptureable membrane that contacts the opening in the metal support disk will rupture when the cell pressure rises to a predetermined level. The rupturable membrane may be made of nylon or polypropylene. However, another preferred material for the insulating sealing disk has been determined to be a polyetherurethane material, particularly a polytetramethylene etherurethane material. Such polyether urethanes are thermoplastic materials that have elastomeric properties. Polyether urethane has alkali resistance and high durability. In the end cap assembly of the present invention, since the direction of the downward inclined arm of the metal support disk is inclined, the gas vent opening can be made larger. The undercut groove in the ruptureable membrane makes the membrane thinner at the rupture location, ie at the bottom of the groove. This, in turn, reduces the design burst pressure and concomitantly reduces the wall thickness of the battery housing, eg, between about 0.10 mm (4 mils) and 0.30 mm (12 mils). And thereby increase the battery internal volume available for the anode and cathode active materials. For example, the end cap assembly of the present invention allows the wall thickness of the battery housing to be between 0.10 mm (4 mils) and 0.20 mm (8 mils) for AA and AAA size batteries. And for D size batteries, it can be between about 0.25 mm (10 mils) and 0.30 mm (12 mils).

  The insulating sealing disk for alkaline batteries may be an injection molded plastic material such as nylon or polypropylene that is durable and corrosion resistant in an alkaline environment. However, it has been determined to be advantageous to form an insulating sealing disk with a polyetherurethane material. The polyetherurethane material available as the PELLETHANE 2103 series from Dow Chemical Co. should be the preferred polyetherurethane material series for alkaline battery sealing disks. The PELLETHANE 2103 series is a polyether urethane with repeating segments of tetramethylene ether and is therefore a polytetramethylene ether urethane material. Such polyether urethanes can be formed as a reaction product of polytetramethylene glycol and diisocyanate to form a polytetramethylene ether urethane material. The softness or hardness of the material may be controlled by the number of repeating units of polytetramethylene ether in the glycol reactant. A preferred polyetherurethane for the insulating sealing disk is available from Dow Chemical Company under the trademark PELLETHANE 2103-80AE. PELLETHANE 2103-80AE polyether urethane is a polytetramethylene ether urethane material having an ultimate tensile strength of 34.5 MPa (5000 psi) and an ultimate elongation of 600%. Polyether urethane materials are chemically resistant to alkali, like nylon. However, polyether urethane is a thermoplastic material having rubber-like elasticity (rubber-elastic thermoplastic resin), while nylon is essentially a thermoplastic resin having no rubber-like elasticity. Thus, the polyether urethane material is rubbery and more flexible than nylon.

  The ultimate tensile strength S of the polyether urethane material is lower than the ultimate tensile strength of nylon 66. That is, a polyetherurethane membrane designed to rupture between about 3.45 MPa (500 psig) and 6.89 MPa (1000 psig) for a given low pressure, eg, AA size alkaline battery, is a target rupture. In order to achieve pressure, it does not require as thin a film thickness as nylon. This is one advantage because at low levels of film thickness, for example, at a level of about 0.10 mm or less, it becomes more difficult to mold the film. Also, the lower ultimate tensile strength S of the polyetherurethane material for the insulating sealing disk is that the metal support for a given target burst pressure of the burstable membrane and a given thickness of the membrane. This means that the size of the contact vent opening in the disc can be made smaller. This allows the second vent opening to be included in the structure of the metal support disk without significantly impairing the structural integrity of the metal support disk. Due to the presence of the second vent opening in the metal support disk, even if the first vent opening in the metal support disk is clogged, it is more certain that the battery will be properly vented from the inside. It becomes. Polyether urethane materials also absorb less moisture than nylon 66 when exposed to hot and humid conditions. This also means that when the insulating sealing plug (insulating sealing disk 20) is made of a polyether urethane material instead of nylon 66, it is less likely that water will enter the battery from the outside environment. To do.

  The peripheral edge of the insulating sealing disk contacts a portion of the inner surface of the housing. Another important advantage of using the structure of polyether urethane material for the insulating sealing disk is that the edge of the housing (casing) is crimped onto the insulating sealing disk and then the periphery of the insulating sealing disk The edge is kept in close conformity with the housing surface it contacts. This is a result of the flexibility or rubbery elasticity and softness of the polyetherurethane material. Such uniform surface-to-surface compatibility between the edge of the insulating sealing disk and the edge of the housing persists over time. This seals a separate sealing film (eg asphalt or polyamide sealing film) to ensure a leak-free surface-to-surface seal between the insulating sealing disk and the housing surface There is no need to apply between the peripheral edge of the disk and the inner surface of the housing. Of course, this does not exclude the addition of such a sealing coating to increase the level of sealing protection between the peripheral edge of the insulating sealing disk and the housing. For example, some polyether urethanes may be made harder than the preferred PELLETHANE 2103-80AE, and applying such a separate sealing coating between the insulating sealing disk and the housing The use of a harder polyether urethane material such as this may be more beneficial. The polyetherurethane material can be advantageously used to form an insulating sealing plug or insulating sealing disk for alkaline batteries, regardless of the configuration of the thin-walled portion or ruptureable membrane portion therein.

  The metal support disk preferably has a substantially flat central portion with a centrally located opening. Preferably, a pair of diametrically opposed openings of the same size are arranged in the downwardly extending wall of the metal support disk. After the battery active component is inserted, the end cap assembly is inserted into the open end of the battery housing. The peripheral edge of the metal support disk and the peripheral edge of the overlying end cap are within the peripheral edge of the insulating sealing disk. The edge at its open end of the housing is then crimped onto the peripheral edge of the insulating sealing disk. Next, the edge of the insulating sealing disk is simultaneously crimped onto both the peripheral edge of the metal support disk and the peripheral edge of the overlying end cap, so that the end cap and the metal support disk are insulated and sealed. Stablely fixed in place on the disc. Thus, the insulating sealing disk, metal support disk, and overlying end cap are secured within the open end of the housing, thereby closing the battery housing. Surprisingly, the peripheral edge of the insulating sealing disk is tightly crimped onto both the edge of the metal support disk and the edge of the end cap so that both edges are held within it. In order to achieve this, sufficient crimping force must be applied during crimping, but the downwardly extending wall of the insulating disk is flush or nearly flush with the downwardly extending wall of the overlying metal support disk. Maintained in a certain state. That is, the downward extending wall portion of the insulating sealing disk is flush with or substantially flush with the downwardly extending wall portion of the metal support disk on it, so that the crimping force does not hinder. .

  The end cap assembly of the present invention has an elongated anode current collector that has a central opening in the metal support disk so that it can be welded directly to the lower surface of the end cap. It has a penetrating head. The head of the anode current collector is preferably welded directly to the underside of the end cap by electrical resistance welding. No other welding of the components of the end cap assembly is necessary. Laser welding need not be used anywhere in the battery assembly, thus making the battery assembly process more efficient.

  With respect to the orientation of the rupturable membrane in contact with the opening in the metal support disk and the use of the preferred undercut groove in the insulating seal to form a portion of the rupturable membrane, the end cap assembly of the present invention The end cap assembly of the solid and the design shown in US Pat. No. 6,887,614 B2 (Duprey) assigned to the assignee of the present invention has several common features. . However, the end cap assembly of the present invention represents an improvement over the Duprey patent. In the end cap assembly of the present invention, the end cap and battery as shown in FIG. 3 of the Duprey patent and as described in column 9, lines 36-51 of that patent. The use of insulating washers between the housing shoulders is eliminated. Thereby, the improved end cap assembly has fewer components. Instead, in the present invention, the peripheral edge of the insulating sealing disk is crimped onto the edge of the end cap and the edge of the underlying metal support disk so that both the metal support disk and the end cap are connected to the battery. Keep tightly fixed in place in the housing. This prevents the end cap from being tampered with, i.e. the edge of the end cap is separated from the housing by an insulating washer, so that the end cap is not easily removed by removing the edge from the battery. . Also, the end cap assembly of the present invention, as shown in FIG. 3 in the Duprey patent, first welds the anode current collector to the underside of the metal support disk and then welds the metal support disk to the end cap. There is no need to do it. In the end cap assembly of the present invention, the head of the anode current collector is welded directly to the end cap. No welding is required between the metal support disk and any other components, thus simplifying battery assembly.

The invention will be further understood with reference to the drawings.
FIG. 3 is a pictorial cutaway view of the end cap assembly of the present invention. FIG. The exploded view which shows the component of the end cap assembly of this invention. The top perspective view of an insulation sealing disk. The top perspective view of a metal support disk. The top perspective view of an end cap.

A preferred structure for the end cap assembly 14 of the present invention is shown in FIG. The end cap assembly 14 of the present invention has particular applicability to an electrochemical cell comprising a cylindrical housing 70 having an open end 15 and an opposite closed end, where the end cap assembly The solid 14 is inserted into the open end 15 to seal the battery. The end cap assembly 14 is particularly applicable to standard AAA (44 × 9 mm), AA (49 × 12 mm), C (49 × 25 mm), and D (58 × 32 mm) size cylindrical alkaline batteries. . The end cap assembly 14 is particularly useful for smaller size alkaline batteries, such as AAA and AA size batteries, but may be advantageously used in C and D size batteries as well. An alkaline battery, such as battery 10 (FIGS. 1 and 1A), desirably includes an anode 140 that includes zinc particles and a cathode 120 that includes MnO ₂ , and an electrolyte permeable separator 130 therebetween. It has. The anode 140 and cathode 120 typically include an aqueous potassium hydroxide electrolyte. The anode 140 may contain zinc particles, the cathode 120 may contain nickel oxyhydroxide, and the anode and cathode may contain an aqueous potassium hydroxide electrolyte.

  The end cap assembly 14 of the present invention comprises a metal support disk 40, an insulating sealing disk 20 below it, and a current collector 80 that contacts the anode 140 through the central opening 24 of the sealing disk 20. I have. A separate metal terminal end cap 60 is stacked on the metal support disk 40 as shown in FIGS. After the cathode 120, separator 130, and anode 140 are inserted into the housing 70, the end cap assembly 14 is inserted into the open end 15 of the housing. A peripheral edge 72 of the housing 70 is crimped onto the peripheral edge 28 of the insulating sealing disk 20. The peripheral edge 28 of the insulating sealing disk 20 is then crimped onto both the peripheral edge 66 of the end cap 60 and the edge 49 of the metal support disk 40. In the crimping process, a radial force can be applied to cause the edge 66 of the end cap 60 to bite into the peripheral edge 28 of the insulating sealing disk 20. Further, the edge 49 of the metal support disk 40 can bite into the edge 28 of the insulating sealing disk 20.

  The metal support disk 40 (FIGS. 1 and 4) preferably has a substantially flat central portion 43 with a centrally located opening 41 therein. The metal support disk 40 is preferably formed of a single metal structure disk having a convoluted surface. A portion of the metal support disk 40 has a downwardly inclined wall 45, and there is at least one vent opening 48 extending through the downwardly inclined wall 45. The metal support 40 is made of a conductive metal having good mechanical strength and corrosion resistance, such as cold rolled steel with nickel plating, stainless steel, or low carbon steel. The metal support disk 40 is preferably made of carbon steel having a convoluted surface with a thickness of about 0.50 mm. Preferably, as best shown in FIG. 4, a pair of diametrically opposed pairs of vent openings 48 of the same dimensions are disposed in the downwardly extending wall 45 of the metal support disk 40. When the battery is viewed from a vertical position with the end cap assembly 14 facing upward, the downwardly extending wall 45 of the metal support disk 40 is located above the wall 45 from a high point 45a on the wall 45 of the support disk 40. Extends downward toward the inside of the battery. The downwardly extending wall 45 of the support disk 40 is preferably straight in the downward inclination direction, but may have a slightly convex surface profile (outward ridge) when viewed from the outside of the battery. it can. The downwardly extending surface 45 terminates at a peripheral edge 49.

  When viewed from a vertical position with the end cap assembly 14 facing up, the insulating sealing disk 20 (FIGS. 1 and 3) has a convoluted surface with a downwardly extending wall 26, A portion of the surface overlaps and contacts the opening 48 in the metal support disk 40. When the battery is viewed from a vertical position with the end cap assembly 14 up, the wall 26 of the sealing disk 20 extends downward from a high point 26a on its surface to a low point 26b on its surface. . The surface 26 of the insulating disk 20 is preferably straight in the downward tilt direction (i.e. does not protrude inward or outward), but has a slightly convex surface profile when viewed from the outside of the battery. It may be. The downwardly extending surface 26 terminates in a peripheral edge 28 that extends upward.

  The portion of the downwardly extending surface 26 below the opening 48 of the metal support disk 40 (FIG. 1) has on its inner surface an undercut groove 210 facing the cell interior. The groove 210 has an open end and a closed bottom on the opposite side. The bottom of the groove forms a thin ruptureable membrane 23. The rupturable membrane 23 contacts the opening 48 of the metal support disk 40. As the gas pressure in the cell increases, the rupturable membrane 23 penetrates through the opening 48 and ruptures, thereby causing the head space 18 above the membrane 23, ie, the membrane 23 and the end caps thereon. Release gas to the space between 60. The gas then proceeds to the external environment through a vent opening 65 in the end cap 60 (FIGS. 1 and 5). Preferably, the downwardly extending wall 26 of the insulating disk 20 is flush with the inner surface of the downwardly extending wall 45 of the metal support disk 40 during assembly. Surprisingly, there is sufficient force to ensure that the peripheral edge 28 of the insulating sealing disk 20 is tightly crimped onto both the edge 49 of the metal support disk and the edge 66 of the end cap. Although it must be applied during crimping, the downwardly extending wall portion 26 of the insulating disk 20 is maintained flush or substantially flush with the downwardly extending wall portion 45 of the metal support disk 40. That is, the crimping force does not release the downwardly extending wall portion 26 of the insulating disk 20 from being substantially flush with the downwardly extending wall portion 45 of the metal support disk 40. The crimping force does not create an average space of more than about 0.50 mm between the downwardly extending walls 26 and 45, and typically the crimping force is between the downwardly extending walls 26 and 45. No space exceeding about 0.35 mm on average is generated during the period. The crimping force typically can create an average space between the lower extending walls 26 and 45 of between about 0.1 mm and about 0.5 mm.

  The groove 210 preferably extends circumferentially along the inner side 220 of the downwardly extending wall 26, as best shown in FIGS. The groove 210 preferably forms a thin-walled portion 23 that extends along the inner side (lower side) of the downwardly extending wall 26 of the insulating sealing disk 20 (FIG. 1). The surrounding groove 210 (FIG. 1) forms a thin portion, that is, the surrounding film 23 at the bottom of the groove 210. The thin-walled portion 23 forms a rupturable membrane that faces and preferably contacts the downwardly extending wall 45 of the metal support disk 40, as shown in FIG. One or more openings 48 may be present in the downwardly extending wall 45 of the metal support disk 40 (FIGS. 1 and 4). Preferably, as shown in FIG. 4, two openings are present on the surface of the downward extending wall 45. If two openings 48 are used, they are preferably of approximately the same size and are arranged diametrically opposite each on the downwardly extending wall 45 (FIG. 4). The portion of the surrounding thin film 23 that extends just below the vent opening 48 forms a burstable portion. As the gas in the battery increases to a predetermined level, the portion of the membrane 23 just below the opening 48 extends into the opening and eventually ruptures under tension to release the gas in the battery. The internal pressure of the battery is immediately reduced as gas flows out through the vent cap opening 65 of the overlying end cap.

  The opposing groove walls 212a and 212b, which define the depth of the undercut groove 210, need not be curved in a particular shape. However, for ease of manufacturing, the groove walls 212a and 212b can be oriented vertically and the mouth of the groove 210 is more than the bottom of the groove (the rupturable membrane portion 23). You may incline so that it may become wide. Since the membrane is preferably intended to rupture by tension rather than shear, the angle of 212a does not contribute to the rupturability of membrane 23. The walls 212a and 212b can advantageously be perpendicular to the rupturable membrane 23 at the bottom of the groove 210 and also obtuse with the rupturable membrane 23 as shown in FIG. Can be formed. Alternatively, the groove walls 212a and 212b are formed of flat or curved surfaces. Desirably, the walls 212a and 212b each form a flat surface that forms an obtuse angle with the rupturable membrane 23, preferably between about 120 and 135 degrees, and thus the open end of the groove 210. Is slightly wider than the bottom of the groove forming the film 23. According to such a preferred embodiment, the enclosing groove 210 is given a trapezoidal shape as shown in FIG. Such an outer shape is desirable from the viewpoint of facilitating manufacture by injection molding, and does not affect the burstability of the film 23.

  The downwardly extending wall 26 and the rupturable membrane portion 23 therein are preferably inclined at an acute angle (an angle less than 90 °) from the central longitudinal axis 190 of the battery, as shown in FIG. In such an outer shape, the downwardly extending wall portion 26 and the film portion 23 inside thereof are not parallel to the central longitudinal axis of the battery. Preferably, the downwardly extending wall 26 is inclined at an acute angle between about 35 and 80 degrees from the central longitudinal axis 190 (FIG. 1). Similarly, the downwardly extending wall 45 of the support disk 40 is preferably inclined at the same acute angle as the downwardly extending wall 26 of the sealing disk 20, ie, between about 35 and 80 degrees from the central axis 190. ing. Therefore, when the support disk 40 is placed on the sealing disk 20, the lower extending wall portion 45 of the supporting disk 40 comes into contact with and is flush with the lower extending wall portion 26 of the sealing disk 20. A possible membrane 23 contacts the opening 48. As indicated above, metal may be used in spite of the need for greater crimping force to simultaneously crimp sealing edge 28 onto both end cap edge 66 and metal support edge 49. It was determined that the lower extending wall 45 of the support disk was maintained flush (or substantially flush) with the lower extending wall 26 of the sealing disk. The downwardly extending wall 45 of the metal support disk 40 is tilted and oriented to create a larger diameter opening 48 in the downwardly extending wall 45 for a given overall height of the support disk 40. Is possible. This allows a given thin thickness of the membrane 23 to rupture at a lower threshold pressure, thereby reducing the wall thickness of the battery housing 70. As the wall thickness of the housing 70 is reduced, the internal volume of the battery available for the anode and cathode active materials increases, thereby increasing the capacity of the battery.

When there is no groove for forming a rupturable film in the sealing body, that is, the entire portion of the wall portion 26 that is inclined downward and in contact with the opening 48 has a uniform and constant thickness. If forming a, in order to apply the approximation, the desired burst pressure P _R, the radius "R" of the vent apertures 48, the thickness of the constant thickness of the resulting film "t" The following relationship has been determined: Here, “S” is the ultimate tensile strength of the burstable material. Even if there is a groove forming a rupturable membrane, the following formula helps to determine the burst pressure.

P _r = t / R × S (I)
The insulating sealing disk 20 may be formed of a single structure of a plastic insulating material. In the embodiment of the end cap assembly 14 shown in FIG. 1, the rupturable membrane 23 in the sealing disk 20 contacts an opening 48 in the metal support disk 40. The insulating sealing disk 20 may be molded by injection molding nylon having durability and corrosion resistance. However, it has been determined that it is advantageous to form the insulating sealing disk 20 with a polyetherurethane material. Preferred polyetherurethane materials may be selected from PELLETHANE 2103 series polyetherurethanes from Dow Chemical Co. PELLETHANE 2103 series polyether urethanes are thermoplastic materials that exhibit rubber-like elasticity. PELLETHANE 2103 series polyether urethanes generally have an ultimate tensile strength lower than that of nylon 66 (ASTM D412 test) and much higher than nylon 66, greater than 200%, typically 300 % Ultimate elongation (ASTM D412 test). (Nylon 66 has an ultimate elongation of about 90%.) Such PELLETHANE materials are thermoplastic (soften when exposed to heat but return to their original state when cooled), yet It also exhibits rubbery elasticity. That is, the PELLETHANE material is a “rubber elastic thermoplastic material”. In contrast, nylon is a thermoplastic material but does not exhibit rubbery elasticity. Thus, the term “rubber-elastic thermoplastic material” as used herein also has an ultimate elongation greater than about 200%, thereby imparting a rubbery elasticity to the thermoplastic material. It shall mean molecular material.

  A preferred polyetherurethane for the insulating sealing disk 20 is available from Dow Chemical Company under the PELLETHANE 2103-80AE trademark designation. (80AE represents 80 Shore in ASTM Shore A hardness tester. E is a medical grade certification mark.) PELLETHANE 2103-80AE polyetherurethane has an ultimate tensile strength of 34.5 MPa (5000 psi) and 600%. The ultimate elongation is Another polyether urethane that can be advantageously used for the insulating sealing disk 20 is available under the trademark PELLETHANE 2103-65D. (65D represents 65 Shore in the ASTM Shore D hardness scale.) PELLETHANE 2103-65D has an ultimate tensile strength of 39.6 MPa (5750 psi) and an ultimate elongation of 360%. However, the PELLETHANE 2103-80AE material is somewhat softer than the PELLETHANE 2103-65D material and is therefore more preferred as a constituent material for the sealing disk 20. Polyether urethane materials, like nylon, are chemically resistant to alkali. However, polyether urethane is a thermoplastic material having rubber-like elasticity, while nylon is essentially a thermoplastic material having no rubber-like elasticity. Polyether urethane materials are rubbery and more flexible than nylon. For example, PELLETHANE 2103-80AE has an ultimate elongation of 600%, while nylon 66 has an ultimate elongation of 90%. Therefore, in comparison, nylon is a hard thermoplastic resin.

  As indicated above, the ultimate tensile strength S of the polyether urethane material is lower than the ultimate tensile strength of nylon. For example, PELLETHANE 2103-80AE polyether urethane has an ultimate tensile strength of 34.5 MPa (5000 psi), while nylon 66 is between about 48.26 MPa (7000 psi) and 75.83 MPa (11000 psi). Has ultimate tensile strength. That is, a polyether urethane ruptureable membrane designed to rupture between about 3.45 MPa (500 psig) and 6.89 MPa (1000 psig) for a given low pressure, eg AA size alkaline battery. In order to achieve such a bursting pressure, a film thickness as thin as nylon is not required. As a result, it is advantageous to form a ruptureable film of polyether urethane compared to nylon, which forms a very thin ruptureable film with a level of, for example, 0.1 mm or less. This is because it becomes more difficult to do.

Also, the lower ultimate tensile strength S of the polyetherurethane material for the insulating sealing disk 20 is that for a given target burst pressure _{Pr of} the membrane 23 and a given thickness t of the membrane 23. This means that the radius R of the venting opening 48 in contact in the metal support disk 40 can be made smaller (see equation I above). As a result, the second vent opening 48 can be included in the structure of the metal support disk 40, for example, in the downwardly extending wall 45 of the metal support disk 40. The presence of the second gas vent opening further ensures that the gas inside the battery is properly vented. That is, when the first vent opening 48 is clogged, the membrane 23 is nevertheless another (second) vent opening 48 disposed in the inclined wall 45 of the metal support disk 40. Burst against. If the insulating sealing disk is made of a polyetherurethane material, a smaller vent opening 48 in the metal support disk 40 can be used so that the metal support disk 40 has the same number, but Compared to the same metal support disk with a larger size vent opening, it is more robust.

  Polyether urethane materials also absorb less moisture than nylon 66 when exposed to hot and humid conditions. This also means that when the sealing disk 20 is formed of a polyether urethane material instead of nylon 66, the possibility of moisture entering the battery from the outside environment is less. When other alkali resistant thermoplastics such as nylon or polypropylene are used for the insulating sealing disk 20, a sealing coating such as asphalt or polyamide coating is applied to the peripheral edge 28a of the sealing disk and the inside of the housing 70. Often applied between the surface or between the anode current collector 80 and the hub 22 of the insulating sealing disk 20.

  Another important advantage of using polyether urethane, such as PELLETHANE 2103-80AE, for the insulating sealing disk 20 is that it provides a distinction between the peripheral edge 28a of the sealing disk 20 and the inner surface of the casing 70. There is no need to apply the sealing coating film. Further, it is not necessary to apply a sealing material between the anode current collector 80 and the hub 22 of the insulating sealing disk 20.

  The polyether urethane material available from Dow Chemical Co. as the PELLETHANE 2103 series has been determined to be a preferred series of polyether urethane materials for the sealing disk 20 of alkaline batteries. As described above, PELLETHANE 2103-80AE was determined to be a more preferred material in this series for the insulating sealing disk 20 of alkaline batteries. The PELLETHANE 2103 series is a polyether urethane containing repeating segments of tetramethylene ether and is therefore a polytetramethylene ether urethane.

Such polytetramethylene ether urethane can be formed as a reaction product of tetramethylene glycol and diisocyanate as follows.

  The degree of softening or hardness of the polytetramethylene ether urethane may be controlled by changing the number of repeating units “m” of tetramethylene in the polyether segment. The diisocyanate may have a group “R” selected from aromatic, aliphatic, or cycloaliphatic, for example, as shown in US Pat. No. 4,394,491. The molecular weight of the polymer is high enough to have useful physical properties. The molecular weight of the polyetherurethane (II) is a function of the number m of polytetramethylene segments and the total number n of repeating units. A common aromatic diisocyanate that can be used in Reaction II above is toluene diisocyanate. Another aromatic diisocyanate that can be used is naphthalene-1,5 diisocyanate. A common aliphatic diisocyanate that can be used in the above reaction is hexamethylene diisocyanate. A common alicyclic diisocyanate that can be used in the above reaction is cyclohexane-1,4 diisocyanate.

  The repeating segment of the polyether in the polyurethane product preferably includes tetramethylene ether formed by using tetramethylene glycol as a reactant with diisocyanate, as shown in Reaction II above. Other glycols may be used as reactants, thus providing other types of ether repeating units, ie units other than tetramethylene ether, to the polyurethane product. For example, the glycol used in the above reaction is ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, It may be selected from 1,5-pentanediol, hexanediol, 1,7-heptanediol, glycerol, and 1,1,1-trimethylolpropane. Also, the repeating segments of the polyether in the polyurethane product may be formed from a polyalkylene polyether polyol. Such polyols may be prepared from other starting materials such as tetrahydrofuran and alkylene oxide tetrahydrofuran copolymers, epihalohydrins such as epichlorohydrin, and aryl alkylene oxides such as styrene oxide. Other polyols that may be used with diisocyanates as reactants to form polyetherurethane products are shown in US Pat. No. 4,394,491.

Degassing burst test and leak test of alkaline batteries using polyether urethane sealing disk The effectiveness of using an insulating sealing disk 20 molded of polyether urethane material was demonstrated in the following tests. The A zinc / MnO ₂ alkaline battery of the same AA size was manufactured as shown in FIG. 1 with the configuration of the end cap assembly 14 as shown in FIG. Therefore, the peripheral edge 28 a of the insulating sealing disk 20 was in contact with a part of the inner surface of the housing 70. A polyether urethane material available under the trademark PELLETHANE 2103-80AE, which is a polytetramethylene ether urethane from Dow Chemical Co. Molded with As shown in FIG. 1, there is a circumferential groove 210 that forms a ruptureable membrane 23 in the downwardly extending wall 26 of the sealing disk. The width of the groove 210 was about 0.5 mm. The rupturable membrane 23 at the bottom of the groove 210 had a thickness of about 0.15 mm. As shown in FIG. 1, two diametrically opposed vent openings 48 were present in the metal support disk 40. In the leak test, both vent openings 48 had a diameter of about 1.8 mm.

  In the membrane rupture test, the same ruptureable membrane 23 having a thickness of about 0.15 mm was used with a circumferential groove 210 having a width of about 0.5 mm. Moreover, there existed gas vent openings 48 of the same size opposed in the diameter direction. However, in some batteries, the diameter of the vent opening is 1.0 mm in diameter, other batteries both have a vent opening 48 with a diameter of 0.9 mm, and other batteries are Both had openings with a diameter of 0.8 mm.

  No type of sealing coating was applied to the area between the peripheral edge 28a of the insulating sealing disk and the peripheral edge 72 of the casing 70 in contact therewith. In addition, no sealing film of any kind was applied to the region between the anode current collector 80 and the hub 22 of the insulating sealing disk 20. The cell was tested for proper rupture of the membrane 23 when the gas pressure in the cell increased.

  In another test, a new AA battery was subjected to a leak test. The AA battery was first subjected to a 12-cycle temperature stress test (TST). The battery was then inspected for leaks. After the 12 cycle temperature test was completed, the same cell was then subjected to a 12 week environmental test and then again checked for leaks.

Rupture Degassing Pressure AA group of zinc / MnO ₂ alkaline cells was tested for good rupture of the rupture membrane 23 described above made of PELLETHANE 2103-80AE material. The rupturable membrane 23 had a thickness of about 0.15 mm. The width of the circumferential groove 210 was about 0.5 mm. Two diametrically opposed vent openings 48 of the same size were present in the metal support disk 40. In the first group of batteries, the vent opening 48 has a diameter of 1.0 mm, and in the second group of batteries, both vent openings 48 have a diameter of 0.9 mm, and the third In the group of cells, both vent openings 48 had a diameter of 0.8 mm. The battery was subjected to overuse conditions, thereby increasing the gas pressure within the battery. The gas pressure in the cell was increased until the PELLETHANE membrane 23 was ruptured, thereby allowing the gas to flow out through the vent opening 48. The gas then advanced to the outside world through an opening 65 in the end cap 60. The gas pressure in the cell is about 8.07 MPa (1170 psi) average for a 1.0 mm diameter vent opening, about 7.89 MPa (1145 psi) for a 0.9 mm vent opening, 0 diameter The membrane 23 ruptured well when an average value of about 9.10 MPa (1320 psi) was reached with a .8 vent opening. The battery was disassembled. Inspection confirms that the portion of the membrane 23 that was in contact with the vent opening 48 has completely ruptured without clogging the vent opening, and thus gas has flowed out of the cell through the vent opening 48. did.

12-cycle thermal stress test (TST)
A new AA battery (FIG. 1) having a sealing disk 20 molded of PELLETHANE 2103-80AE material was subjected to a 12-cycle thermal stress test. No separate sealing coating was applied between the peripheral edge 28a and the inner surface of the housing 70. Further, the sealing coating film was not applied between the hub 22 of the insulating sealing disk 20 and the anode current collector 80. The procedure for each cycle of this test involved exposing the assembled AA battery to heating for 1 hour in an oven maintained at 71 ° C. by forced hot air. The battery was then removed from the oven and placed directly in the freezer. The battery was left in a freezer at -29 ° C for 1 hour. The battery was removed from the freezer and placed on a table and maintained on the table at ambient temperature (21 ° C.) for 1 hour. This completes one cycle. The battery was then placed back in the 71 ° C. oven for 1 hour to start a new cycle. The battery was thus subjected to 12 cycles. The battery was inspected for leaks after the 12 cycle test procedure was completed.

  Of the seven AA batteries tested, no leakage was observed in any of the batteries.

12-week environmental test Following the 12-cycle thermal stress test (TST) described above, the same cell was then subjected to a further test, ie a 12-week environmental test. After the cell was subjected to 12 cycles of temperature stress testing, the same cell was then left in open ambient air at about 21 ° C. for a duration of 1 week. The battery was then inspected for leaks.

  Of the seven AA batteries tested, no leakage was observed in any of the batteries. These results show the effectiveness of the polyether urethane material as the constituent material of the sealing disk. In particular, as indicated above, no kind of sealing coating is applied to the area between the sealing disk 20 and the casing 70 or between the anode current collector 80 and the hub 22 of the sealing disk. These results are impressive. The very effective sealing properties of the polyetherurethane material (PELLETHANE 2103-80AE) are due to the numerous properties of this material present in combination. First, this material is resistant to corrosion by alkaline electrolytes. This material, unlike nylon or polypropylene, has rubbery elasticity. When the casing edge 72 of the housing is crimped onto the edges of the insulating sealing disk 20 and the end cap due to the rubber-like elasticity of the polyether urethane insulating sealing disk 20, the peripheral edge 28a of the insulating sealing disk 20 is crimped. Permanent conformal surface-to-surface fit between the housing 70 and the edge 72 of the housing 70 is possible. That is, the polyether urethane (PELLETHANE 2103-80AE) material has rubbery elasticity and a relatively soft texture, so that it is between the edge 28a of the insulating sealing disk and the edge 72 of the casing. The contact and fit between the surfaces does not become loose or weak once the casing edge 72 is crimped onto the sealing disk edge 28a. Therefore, even if the battery is subjected to the two successive leak tests described above, there is no possibility that the alkaline electrolyte will penetrate into the area between the insulating sealing disk and the casing.

  In this regard, the advantages over alkaline battery sealing discs made of conventional nylon or polypropylene, which are harder and therefore more likely to eventually separate from close and uniform contact with the casing edge 72, It is clear that the polyether-urethane sealing disk has rubbery elasticity. As a result of the rubbery elasticity of the insulating sealing disk 20 formed of polyether urethane (PELLETHANE 2103-80AE), as demonstrated in the above test, the insulating sealing disk edge 28a and the casing edge 72 The tight, conformal surface adhesion between the two surfaces is maintained even when no separate sealing coating is applied between the two surfaces. This, of course, does not exclude the use of such a separate sealing coating for further protection against leaks. For example, an asphalt sealing or polyamide coating or other sealing coating may still be applied between the sealing disk edge 28a and the casing edge 72 for additional protection against leakage. May be. Such a sealing coating may be beneficial when other grades of polyetherurethane materials are used, such as PELLETHANE 2103-80D, which is as soft and non-elastomeric as PELLETHANE 2103-80AE.

  The polyetherurethane materials described herein have been used as an example in certain embodiments of the insulating sealing disk 20 as shown in FIGS. The insulating sealing disk 20 has a circumferential groove 210, and a thin region of the material remaining at the bottom of the groove forms a ruptureable film 23. For example, as shown in U.S. Pat. No. 4,237,203 and U.S. Pat. No. 6,991,872, including a thin portion that forms a rupturable membrane in the form of slits or grooves in an insulating disk. Other configurations of an alkaline battery insulation sealing disk have been disclosed in the art. Such thin-walled portions or ruptureable membranes within the insulating disk are designed to rupture when the gas pressure in the cell increases to a predetermined level. As shown in U.S. Pat. No. 3,314,824, a tapered or other protruding member can be directed over the rupturable membrane to assist in rupturing the membrane. The rupturable membrane is a thin material in an insulating disk as shown in US Pat. No. 4,537,841, US Pat. No. 5,589,293, and US Pat. No. 6,042,967. Can be in the form of one or more “islands”.

  Regardless of whether the portion of the rupturable membrane inside the insulating disk of the alkaline battery is of a grooved or slit configuration, or of an “island” type configuration, it is described herein. The polyether urethane material that can be used can be used to mold or form an insulating disk of an alkaline battery. Therefore, the polyether urethane material can be used for the construction of an insulating sealing disk of a specific alkaline battery, or for a specific shape or construction of a thin portion in which a ruptureable film is formed. It is not intended to be limited. For example, the housing surface 70 and the sealing disk may have a rectangular or elliptical configuration rather than a cylindrical shape, and may have a prismatic or cubic shape. The groove 210 forming the rupturable film 23 in the insulating sealing disk 20 and the thin portion below it may be of the island type and may be annular or segmented. If a split (discontinuous) groove in the sealing disk 20 and a thin-walled portion 23 underneath are used, they can be curved, whether linear or arcuate in shape. It may be a shape. The polyether urethane material described herein is used to form or form an insulating sealing disk for an alkaline battery in the form of a thin portion inside the disk or a disc that forms a ruptureable film. Or it can be used conveniently regardless of the configuration. The polyetherurethane material may also be useful in forming insulating sealing disks for other battery types, such as batteries having lithium or lithium alloy anodes. Such a battery uses a non-aqueous electrolyte containing a lithium salt dissolved in an organic electrolyte. The degree of usefulness of the polyether urethane material for the sealing disk of such a non-aqueous battery is determined by experiment so as to ensure compatibility between the polyether urethane material and the electrolyte.

  As best shown in FIGS. 1 and 3, the insulating disk 20 has a central boss or hub 22 with an opening 24 in the center. The boss 22 forms the thickest and heaviest part of the disk 20. When the battery is viewed from a vertical position with the end cap assembly facing up, the peripheral edge of the boss 22 terminates in a downwardly extending wall 26, which extends downwardly from the wall 26. It extends downward from an upper high point 26a to a lower point 26b on the wall 26 (FIGS. 1 and 3). Similarly, the peripheral edge of the central portion 43 of the support disk 40 terminates in a downwardly extending wall portion 45, and this downwardly extending wall portion 45 extends from the high point 45 a on the wall portion 45 to the wall portion. It extends downward to a low point 45b on 45 (FIGS. 1 and 4).

  In addition, the rupturable film 23 is arranged closer to the end cap 60 due to the configuration of the insulating sealing disk 20 described above. That is, the internal space in the battery that can be used for the active substance is increased. Due to the location of the rupturable membrane 23 on the downwardly extending wall 26 of the insulating disk 20, gases and other internal components can be passed from the inside of the cell through the opening 48 in the metal support disk after the membrane 23 has ruptured. It becomes possible to proceed directly to the outside world through the opening 65 in the end cap 60 without being obstructed. Such a progression of gas from inside the battery to the outside world is not hindered when the battery is connected to another battery or powered device.

  It was possible to reduce battery gas generation by using multiple gas generation inhibitors. It is desirable to increase the radius of the opening 48 and reduce the thickness of the film having a certain thickness as much as possible. This makes it possible to rupture the membrane at a lower threshold pressure P of the gas raised in the battery if desired. Thus, for a given cell size, there is a practical lower limit on the explosion pressure that is determined by the maximum achievable opening radius and the minimum film thickness. By adding an undercut groove 210 that forms a rupturable film, additional variables are obtained for manipulating the explosion pressure to lower levels, such as the depth and width of the groove.

  In the end cap assembly 14, the ratio between the width of the rupturable membrane (ie, the width of the bottom of the groove 210) and the thickness of the rupturable membrane 23 is typically about 2.5: 1 and 12.2. Between 5: 1. This design of end cap assembly 14 is typically about 1.8 mm and 10 mm (circle diameter) for typical battery sizes between AAA size batteries and D size batteries. An intermediate opening 48 may be provided in the downwardly inclined wall 45 of the metal support disk 40.

  The following lower level burst pressure of membrane 23 is desirable for the end cap assembly 14 of the present invention. For AAA alkaline cells, the target burst pressure of the membrane 23 is desirably between about 6.21 MPa (900 psig) and 12.41 MPaG (1800 psig). For AA alkaline cells, the target burst pressure of the membrane 23 is desirably between about 3.45 MPa (500 psig) and 10.34 MPaG (1500 psig). For C size alkaline cells, the target burst pressure of membrane 23 is desirably between about 2.07 MPa (300 psig) and 3.79 MPaG (550 psig). For D-size alkaline cells, the target burst pressure of membrane 23 is desirably between about 1.38 MPa (200 psig) and 2.76 MPaG (400 psig). Such burst pressure ranges are intended as non-limiting examples. Since the end cap assembly 14 of the present invention can be used at higher and also lower burst pressures, the end cap assembly 14 is intended to be limited to these burst pressure ranges. It will be understood that not.

  For the range of burst pressures indicated above for a given cell size, nickel plated steel housing 70 is typically about 0.15 mm (0.006 inch) and 0.30 mm (0) for AA and AAA. 0.012 inches), preferably between about 0.15 mm (0.006 inches) and 0.20 mm (0.008 inches), and for C and D about 0.20 mm (0 Can have a thin wall thickness between .010 inches and 0.012 inches. Although it is desirable for the wall thickness of the housing 70 to be thinner, this results in an increase in the internal volume of the battery and the use of more anode and cathode materials, thereby increasing the capacity of the battery. Because. The end cap assembly 14 can achieve the burst pressures described above for a given battery size and has the additional function that the end cap 60 provides “tamper proof”. That is, the edge 66 of the end cap 60 is crimped under the peripheral edge 28 of the insulating sealing disk 20 and is not easily removed from the end cap assembly. Therefore, in the design of the end cap assembly 14 of the present invention, the battery contents are likewise very robust and well protected against malicious tampering. In addition, in the end cap assembly 14 of the present invention, the head 87 of the anode current collector nail 80 is welded directly to the underside of the end cap 60. This can be achieved by simple electrical resistance welding. In the end cap assembly 14 of the present invention, there is no need to weld any other battery components and no need for laser welding, thus simplifying the structure of the battery.

  In order to allow a larger sized opening 48 to be used in the context of the end cap assembly described herein, this would result in an insulating sealing wall 26 comprising a rupturable membrane 23. It was determined that it was best achieved by tilting, ie, pointing non-parallel to the longitudinal axis. Preferably, the sealing wall 26 and the metal support surface 45 in contact therewith are inclined downwardly from the longitudinal central axis 190, preferably at an angle between about 35 and 80 degrees. This increases the available surface area for forming the opening 48.

  In harmony with the need to reduce the explosion pressure of the battery, it has been determined that this can be achieved by forming an undercut groove 210 on the inner surface of the downwardly inclined wall 26 of the sealing disk 30. It was. Such an undercut groove 210 may be formed, for example, surrounding the center of the sealing disk 20 during injection molding when forming the sealing disk 20.

By way of a non-limiting example, in a preferred embodiment using an AA size alkaline battery, the rupturable membrane 23 has a gas in the battery between about 3.45 MPa (500 psig) and 10.34 MPa (1500 psig). Can be designed to rupture when raised to level. The rupturable membrane portion 23 below the opening 48 in the metal support disk 40 is advantageously a polyether urethane material, such as PELLETHANE 2103- by Dow Chemical Co. as described above. It is formed of 80AE. Alternatively, the rupturable membrane 23 may be formed of nylon, preferably nylon 66 or nylon 612, but may be formed of other materials such as polypropylene. (Nylon 66 is more cost effective than nylon 612 and is preferred in this regard.) Groove 210 has a width between about 0.08 mm and 1 mm, preferably between about 0.08 mm and 0.8 mm. Can have. The groove 210 preferably extends circumferentially around the inner surface 220 of the downwardly extending wall 26 of the insulating disk 20. A section of the circumferential groove 210 extends just below the opening 48 in the metal support disk 40. Alternatively, the grooves 210 need not be enclosed, but the individual grooves are cut just below the opening 48, leaving portions of the inner surface of the wall 26 between them smooth and uncut. Can be formed as follows. For typical battery sizes between AAA size batteries and D size batteries, the opening 48 is about 1.8 mm, corresponding to an area between about 2.5 mm ² and 78.5 mm ^2. between the 10 mm, typically are of circular shape having a diameter of between 2mm and 9mm corresponding to the area of between about 3.1 mm ² and 63.6 mm ² (diameter circle) obtain. It should be understood that the opening 48 can be of other shapes such as rectangular or elliptical. Also, the openings 48 can be rectangular or polygonal, or irregularly shaped including a combination of straight and curved surfaces. Also, the effective diameter of such a rectangular or polygonal shape or other irregular shape is desirably between about -2 mm and 9 mm. The effective diameter of such a shape can be defined as the minimum distance across any such opening.

The target burst pressure is between about 3.45 MPa (500 psig) to 10.34 MPa (1500 psig) for AAA batteries, or about 6.21 MPa (900 psig) to 12.41 MPa (1800 psig) for AAA size batteries. The ratio of the groove width (the width of the film 23 at the bottom of the groove) and the thickness of the rupturable film 23 is preferably between about 2.5: 1 and 12.5: 1. is there. According to this range of ratios, the width of the groove at the bottom of the groove is desirably between about 0.1 mm and 1 mm, preferably between about 0.4 mm and 0.7 mm, and the thickness of the rupturable membrane 23 The thickness is between about 0.08 mm and 0.25 mm, preferably between about 0.10 mm and 0.20 mm. The opening 48 can have a diameter typically between about 1.8 mm and 4.5 mm, corresponding to an area between about 2.5 mm ² and 16 mm ² .

  If C and D alkaline cells are used, the rupturable membrane 23 is desirably designed to rupture at lower pressures. For example, for a C size battery, the target burst pressure may be between about 2.07 MPa (300 psig) and 3.79 MPa (550 psig). For D size batteries, the target burst pressure may be between about 1.38 MPa (200 psig) and 2.76 MPa (400 psig). The same ratio of groove width (the width of the film 23 at the bottom of the groove) to the thickness of the rupturable film 23, preferably between about 2.5: 1 and 12.5: 1, is also applicable. is there.

  In general, regardless of the size of the battery, the ratio of the thickness of the rupturable membrane 23 to the thickness of the downwardly extending sealing wall 26 in direct contact with the membrane 23 is less than 1: 2, preferably about 1: 2. It is desirable to maintain it between 1:10, more typically between about 1: 2 and 1: 5. In such embodiments, the thickness of the rupturable membrane 23 is desirably between about 0.08 mm and 0.25 mm, preferably between about 0.1 mm and 0.2 mm. The opening 48 through which the membrane 23 ruptures desirably has a diameter between about 1.8 mm and 10 mm.

  In assembly, after the anode 140, cathode 120, and separator 130 are inserted into the battery housing 70, the end cap assembly 14 is inserted into the open end 14 of the housing. The metal support disk 40 can first be pressed against the insulating sealing disk 20 such that the upper surface 43 of the boss 22 of the sealing disk 20 enters the central opening 41 of the metal support disk 40. The downwardly extending wall portion 26 of the insulating disk 20 is flush with the inner surface of the downwardly extending wall portion 45 of the overlying metal support disk 40. The insulating sealing disk 20 containing the metal support disk 40 therein can then be inserted into the open end 15 of the housing 70. The lower part of the peripheral edge 28 of the insulating sealing body is placed on a circumferential bead 73 in the side wall 74 of the battery housing. The head 87 of the current collector nail 80 is welded to the underside of the end cap 60, preferably by electrical resistance welding.

  The current collector 80 is then inserted through the opening 41 in the metal support disk 40 and then through the central opening 24 in the insulating sealing disk 20 below it. It penetrates into the material of the anode 140. The lower side of the attached end cap 60 is placed on a flat upper surface 43 surrounding the opening 41 of the metal support disk 40. Both the edge 49 of the metal support disk 40 and the edge 66 of the overlying end cap 60 are inside the peripheral edge 28 of the insulating sealing disk 20, as shown in FIG. The edge 72 of the housing 70 is then crimped onto the peripheral edge 28 of the insulating sealing disk 20. Next, the edge 28 of the insulating sealing disk is crimped onto both the edge 49 of the metal support disk 40 and the edge 66 of the end cap 60 so that the end cap 60 and the underlying metal support disk 40 are , And stably fixed in place on the insulating sealing disk 20. Thus, the insulating sealing disk 20, the metal support disk 40, and the overlying end cap 60 are secured within the open end 15 of the housing, thereby closing the battery housing. In order to ensure that the peripheral edge 66 of the end cap 60 fits into the peripheral edge 28 of the insulating sealing disk 20 and the edge 49 of the metal support disk is radially compressed, thereby achieving a seal. A radial compressive force may be applied to the housing 70 during crimping in order to ensure the help. The edge 66 of the end cap 60 cannot be touched by hand, and therefore the end cap 60 is considered to prevent tampering, that is, it cannot be easily removed from the battery assembly.

  In another embodiment of the sealing disk 20, the configuration of the disk is such that after the disk is formed, with the die or knife edge, with or without a thermal jig, of the downwardly extending wall 26 of the sealing disk 20. It can be the same as shown in FIGS. 1 and 3 except that the groove 210 can be formed by stamping or stamping on the lower side 220. In such an embodiment, the sealing disk 20 may be formed by first shaping to obtain a downwardly extending wall 26 of uniform thickness, i.e., without grooves 210. A die having an annular cutting edge can then be applied to the lower surface 220 of the downwardly extending wall 26 of the sealing disk. A groove 210 forming an annular or arcuate cut, less than 1 mm wide, desirably between about 0.08 mm and 1 mm, preferably between 0.08 mm and 0.8 mm, is thus sealed It can be made on the lower surface 220 of the downwardly extending wall 26 of the disk 20. The groove 210 forms a rupturable membrane 23 at the bottom of the groove. The rupturable film 23 formed by the groove 210 forms a weak area on the surface of the downwardly extending wall 220 of the sealing disk. The groove 210 can be made by using a punching die, for example, a die having a raised edge (cutting edge) that is pressed against the underside of the downwardly extending wall 26. By forming the groove 210 in this manner, the film 23 at the bottom of the groove 210 can be formed thinner than when the groove 210 is formed inside the downwardly extending wall portion 26. The groove 210 formed by the stamping die can thus be a rupturable membrane 23 that is very narrow and very thin. The film 23 formed by the groove notch 210 (FIG. 1) adjusts the depth of the notch and then forms the desired thickness of the rupturable film 23 at the bottom of the notch. Can be designed to burst with pressure.

  The film 23 formed by the groove notch 210 contacts the lower side of the downwardly extending wall 45 of the metal support disk 40. A portion of the membrane 23 is below one or more openings 48 in the downwardly extending wall 45 of the metal support disk 40 in the same manner as described in connection with the embodiment shown in FIG. obtain. The groove notch 210 (FIGS. 1 and 3) may not be in the form of a continuous closed circle, but preferably the portion of the groove 210 below the opening 48 is continuous over the entire width of the opening 48. It will be appreciated that the arcuate sections can be sufficiently long to be relevant. In other words, the groove 210 may not extend to the portion 220 (FIG. 1) of the downward extending wall portion 26 that is not on the opening 48.

  In certain embodiments, as a non-limiting example, regardless of the size of the battery, the sealing disk 20 can be made of polyether urethane, such as PELLETHANE 2103-80AE, or nylon 66, and the groove notch 210 Can typically have a width between about 0.08 mm and 1.0 mm, preferably between about 0.08 mm and 0.8 mm. The film 23 formed at the bottom of the groove cut has a ratio between the thickness of the film 23 and the thickness of the downwardly extending wall 26 adjacent to the groove 210 between about 1:10 and 1: 2, preferably The thickness can be between about 1: 5 and 1: 2. In such an embodiment, the thickness of the rupturable membrane 23 is typically between about 0.08 mm and 0.25 mm, desirably between about 0.1 mm and 0.2 mm.

  Polyether urethane or nylon 66 is the preferred material for the insulating disc 20 and the rupturable membrane portion 23 integral therewith, but other materials, preferably polysulfone, polypropylene, or talc, which are preferably resistant to alkali and durable. It should also be understood that plastic materials such as filled polypropylene are also suitable. The combination of the thickness of the membrane 23 and the dimensions of the opening 48 may be adjusted depending on the ultimate tensile strength of the material used and the level of gas pressure at which rupture is intended. It has been found appropriate to use only one opening 48 and one corresponding rupturable membrane 23. However, the downwardly extending wall 45 in the metal support disk 40 can also be provided with a plurality of openings of equal dimensions that contact one or more ruptureable membrane portions 23 underneath. is there. Preferably, two diametrically opposed openings 48 in the metal surface 45 can be used as shown in FIG. This further ensures that the membrane ruptures and venting occurs at the desired gas pressure.

  A typical chemical composition of the anode 140, cathode 120, and separator 130 for the alkaline battery 10 that can be used regardless of battery size is described below. The following chemical plasticity is a typical basic composition for use in a battery having the end cap assembly 14 of the present invention and is therefore not intended to be limiting.

  In the embodiments described above, the exemplary cathode 120 can include manganese dioxide, graphite, and an aqueous alkaline electrolyte, and the anode 140 can include zinc and an aqueous alkaline electrolyte. The aqueous electrolyte contains a conventional mixture of KOH, zinc oxide, and a gelling agent. The anode material 140 may be in the form of a gelled mixture containing anhydrous silver (no mercury added) zinc alloy powder. That is, the battery can have a total mercury content of less than about 50 parts per million of the total weight of the battery, preferably less than 20 parts per million of the total weight of the battery. The battery also preferably does not contain any added amount of lead and is therefore essentially lead-free, i.e. the total lead content is less than 30 ppm, desirably less than 15 ppm of the total metal content of the anode. It is. Such a mixture typically includes an aqueous potassium hydroxide electrolyte, a gelling agent (eg, an acrylic acid copolymer available under the trade name Carbopol C940 from BF Goodrich), A surfactant (for example, an organic phosphate ester surfactant available from Rhone-Poulenc under the trade name GAFAC RA600) can be contained. Such mixtures are given merely as illustrative examples and are not intended to limit the invention. Another representative gelling agent for a zinc anode is disclosed in US Pat. No. 4,563,404.

The cathode 110 is preferably
5-7 with 87-93 wt% electrolytic manganese dioxide (e.g. Trona D by Kerr-McGee), 2-6 wt% (total) graphite, KOH concentration of about 30-40 wt% It can have a composition of 7% to 10% KOH aqueous solution by weight and 0.1% to 0.5% by weight optical polyethylene binder. Electrolytic manganese dioxide typically has an average particle size between about 1 μm and 100 μm, desirably between about 20 μm and 60 μm. The graphite is typically in the form of natural graphite or expanded graphite or mixtures thereof. Graphite can also include graphitic carbon nanofibers alone or mixed with natural graphite or expanded graphite. Such cathode mixtures are intended to be illustrative and are not intended to limit the invention.

Anode material 150 comprises 62% to 69% by weight zinc alloy powder (99.9% by weight zinc containing 200 to 500 ppm indium as alloy and plated material), 38% by weight KOH and about 2% by weight. % KOH aqueous solution containing ZnO; F. A cross-linked acrylic acid polymer gelling agent (for example, 0.5% to 2% by weight) commercially available from BF Goodrich under the trade name “Carbopol C940” and Grain Processing Co. ) Hydrolyzed polyacrylonitrile (between 0.01% and 0.5% by weight) grafted onto the starch backbone, commercially available under the trade name “Waterlock A-221” from Rhône-Poulenc (Rhone-Poulenc) and a dinonylphenol phosphate surfactant commercially available under the trade name “RM-510”. The average particle size of the zinc alloy is desirably between about 30 μm and 350 μm. The bulk density of zinc at the anode (anode porosity) is between about 1.75 g and 2.2 g per cubic centimeter of anode. The volume percent of aqueous electrolytic solution in the anode is preferably between about 69.2 volume percent and 75.5 volume percent of the anode. The battery is the MnO ₂ mA-hr capacity (based on 308 mA-hr per gram of MnO ₂ ) divided by the zinc alloy mA-hr capacity (based on 820 mA-hr per gram of zinc alloy). Can be balanced in a conventional manner such that is approximately 1.

  Separator 130 can be a conventional ionic porous separator made of a cellulosic material. The separator may have an inner layer of a non-woven material of cellulosic fibers or polyvinyl alcohol fibers and an outer layer of cellophane. Such materials are merely illustrative and are not intended to limit the invention. In order to help suppress gas generation, the current collector 80 is brass, preferably brass with tin plating or with indium plating.

  Although the present invention has been described with respect to particular embodiments, it should be understood that variations are possible within the concept of the invention. Accordingly, the invention is not intended to be limited to the specific embodiments described herein, but the scope of the invention is defined by the claims and their equivalents.

Claims (10)

  Electrochemical comprising a housing having an open end, an opposing closed end, and a side wall therebetween, and an insulating sealing plug inserted into the open end of the housing to close the open end An electrochemical battery comprising a positive electrode terminal, a negative electrode terminal, and an alkaline aqueous electrolyte, wherein the insulating sealing plug includes a polyether urethane material.   The battery of claim 1, wherein the insulating sealing plug comprises a polytetramethylene ether urethane material.   The battery according to claim 1, wherein the insulating sealing plug has an elongated conductive current collector passing through the insulating sealing plug, and the current collector is in electrical contact with a battery terminal. .   The housing has a surface facing the interior of the battery, the insulating sealing plug comprises a peripheral edge that contacts a portion of the surface of the housing, and a sealing coating is formed on the sealing plug. The battery according to claim 7, wherein the battery is not provided between a peripheral edge and the surface of the housing.   The battery according to claim 1, wherein the polyether urethane is a rubber elastic thermoplastic material.   The battery of claim 5, wherein the rubber elastic thermoplastic material has an ultimate elongation greater than about 200%.   The battery of claim 1, wherein the polyether urethane material has an ultimate tensile strength less than that of nylon 66 and an ultimate elongation greater than 200%.   The battery of claim 1, wherein the insulating sealing plug comprises a polytetramethylene ether urethane material.   The battery of claim 8, wherein the polytetramethylene ether urethane material is formed from a reaction product of polytetramethylene glycol and diisocyanate.   The insulating sealing plug includes a thin portion integrally formed therein, and the thin portion forms a rupturable membrane that bursts when the gas pressure in the battery rises, and the rupturable membrane is The battery of claim 1, comprising a polyetherurethane material.

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